This invention relates generally to testing foamed cement, especially of types to be used in oil or gas wells.
Various compositions that are to be used in wells are preferably tested before they are used so that the nature of the composition can be known, thereby to determine whether the composition might function as desired down in the high pressure, high temperature environment often encountered in an oil or gas well, for example. Foamed cement is a particular type of composition that is used downhole and that preferably is tested before use. Although the desirability of knowing characteristics of compositions has been known, there is a continuing need for improved methods and devices for testing such compositions, including in particular foamed cement.
A prior type of foamed cement testing has called for the material under test to be transferred under pressure from one device to another. The present invention provides a test method for foamed cement in which there is no transfer of the test composition under pressure from one device to another and in which the equipment is not handled under dangerous pressure, thereby providing a safe test method.
The present invention can be defined as a method of evaluating a foamed cement of a type for use in a well, comprising: rotating a paddle at a first speed in a pressurized foamable cement composition in a receptacle in a high pressure, high temperature chamber such that the foamable cement composition becomes a foamed cement; rotating the paddle at a second speed in the pressurized foamed cement for a selected time period; maintaining the foamed cement static after the selected time period and increasing temperature in the chamber during a foamed cement setting period; thereafter reducing temperature in the chamber and reducing pressure in the chamber; removing the foamed cement in a set condition and the paddle from the chamber; removing the foamed cement in the set condition from the paddle; and testing the removed foamed cement in the set condition.
Another definition of the present invention is as a method of evaluating a foamable cement of a type for use in an oil or gas well, comprising: rotating a paddle at a first speed in pressurized foamable cement disposed in a receptacle in a high pressure, high temperature chamber and continuing rotating until the foamable cement is foamed cement; rotating the paddle at a second speed in the pressurized foamed cement for a selected pump-in time period defined for a cementing job to use the same type of composition as the foamed cement; maintaining the foamed cement static after the selected time period and increasing temperature in the chamber to a selected wellbore temperature for a setting time period such that the foamed cement becomes set cement; slowly reducing temperature in the chamber below the selected wellbore temperature and slowly reducing pressure in the chamber after the setting time period; removing the set cement and the paddle from the chamber after the temperature and pressure are reduced; removing the set cement in pieces from the paddle; and testing each of the pieces of the removed set cement.
Other and further objects, features, and advantages of the present invention will be readily apparent to those skilled in the art when the following description of the preferred embodiments is read in conjunction with the accompanying drawing.